1. Field of the Invention
The present invention relates generally to a gas turbine engine, and more specifically to a turbine stator vane with a dirt separator.
2. Description of the Related Art including information disclosed under 37 CFR 1.97 and 1.98
A gas turbine engine, such as an industrial gas turbine (IGT) engine, includes a turbine with multiple rows or stages or stator vanes that guide a high temperature gas flow through adjacent rotors of rotor blades to produce mechanical power and drive a bypass fan, in the case of an aero engine, or an electric generator, in the case of an IGT. In both cases, the turbine is also used to drive the compressor.
In the turbine section of the gas turbine engine, stages or rotor blades and stator vanes are used to guide the hot gas flow through and react with the rotor blades to drive the engine. To improve engine efficiency, the upstream stages of these airfoils (vanes and blades) are cooled with cooling air to produce convection cooling, impingement cooling, and even film cooling of the outer airfoil surfaces in order to allow for exposure to higher gas flow temperatures. The higher the turbine inlet temperature of the turbine, the higher will be the turbine efficiency and thus the engine efficiency. However, the highest temperature allowed is dependent upon the material properties of these airfoils, especially for the first stage airfoils, and the amount of cooling provided.
Higher levels of cooling can be used for these airfoils. However, since the pressurized cooling air is from the compressor, the more cooling air used from the compressor the more compressed air and work performed by the compressor that is not turned into useful work by the engine. The engine efficiency also decreases due to the extra work performed on compressing the cooling air which is then discharged into the hot gas flow so that no work is performed.
Turbine airfoils that include film cooling holes also suffer from plugging due to dirt particulates in the cooling air that reach a film cooling hole and block it or significantly reduce the amount of cooling air flowing through the semi-blocked hole. Film cooling holes with partially or fully blocked holes will result in a hot spot occurring around the hole. Hot spots lead to high metal temperature problems and erosion problems that significantly reduce the LCF (low cycle fatigue) of the airfoil which decreases the useful life of the airfoil.